1. Field of the Invention
The present invention relates to a method for controlling the recording operation of an ink jet recording apparatus, and more particularly a recording method of applying, in driving a piezoelectric element, a first voltage pulse for retracting the meniscus before the ink droplet formation in a direction opposite to that of the ink droplet emission, and a second voltage pulse for causing ink droplet emission, and an ink jet recording apparatus utilizing said recording method.
2. Related Background Art
In an ink jet recording apparatus, ink is supplied to a recording head, and emission energy generating means provided in said recording head is activated according to the information to be recorded thereby emitting liquid ink from an ink orifice toward a recording medium and forming a record on said medium by means of the emitted ink.
For said energy generating means for forming ink droplet, it is already known that a piezoelectric element for electromechanical conversion or a heater for electrothermal conversion can be generally employed.
For driving an ink jet recording apparatus utilizing a piezoelectric element for the energy generating means, there is already proposed, in the Japanese Patent Publication (examined) No. 3272/1984, a method of applying, to said piezoelectric element, a first voltage pulse for retracting the meniscus in the ink emitting orifice, in a direction opposite to the direction of emission prior to the ink droplet formation, and a second voltage pulse for forming and emitting an ink droplet in succession to said first voltage pulse.
In such an ink jet recording method, it is intended to obtain smaller ink droplets of a precise size and a higher emission speed by applying, to the piezoelectric element, a first voltage pulse to retract the meniscus in the emission orifice prior to the ink droplet formation, and a second voltage pulse in succession.
As the ink emission is conducted by the second voltage pulse while the meniscus is retracted by the application of the first voltage pulse, the amount of ink emission is reduced in comparison with the absence of the first voltage pulse. Also the emission speed increases due to the presence of a meniscus advancing force, caused by the surface tension of the meniscus in the retracted state.
It is therefore possible to obtain smaller ink droplets, thereby forming recording dots with a higher density and a higher precision, by applying a voltage pulse for retracting the meniscus before applying a voltage pulse for ink droplet emission. It is also rendered possible to reduce the ink coagulation at the orifice since a recording head with a relatively large orifice size can be employed.
In addition the higher ink emission speed improves the positional precision of record dots on the recording medium.
However, in such ink jet recording apparatus, the performance of the piezoelectric element and the physical properties of the ink are affected by the circumferential temperature.
In general the piezoelectric element shows a larger displacement for the application of a given voltage, at a higher temperature. On the other hand, the ink viscosity becomes lower at a higher temperature.
Consequently if a fixed voltage pulse is given as the first voltage pulse for meniscus retraction regardless of the temperature, the amount of meniscus retraction becomes larger or smaller than a desired value respectively at a higher or lower temperature.
If such phenomenon is large enough, at a higher temperature, a large meniscus retraction may eventually result in a bubble suction from the outside, leading to unstable ink emission or lack of emission, while, at a lower temperature, a reduced meniscus retraction loses the advantages such as formation of smaller ink droplets and a higher emission speed.
Also the Japanese Patent Publications (unexamined) Nos. 27210/1980, 65566/1980, 65567/1980 and 60261/1981 disclose modification of the driving conditions of the piezoelectric element according to the temperature. However these proposed methods do not employ the first and second pulses explained above, and do not have, therefore, the advantages of the recording method utilizing two pulses.
Consequently the above-mentioned drawbacks cannot be resolved completely by merely modifying the emission pulse in these methods in which an ink emission is made by an emission pulse.